Implantable hearing assistance device with remote electronics unit

ABSTRACT

An implantable hearing assistance system has a subcranially implantable electronics unit that is remotely situated from the ear, such as implanted in the pectoral region, rather than in the mastoid portion of the temporal bone. The increased volume available in the remote electronics unit allows it to carry a power source of increased energy capacity. This improves longevity, allows higher power consumption signal processing capability, and simplifies battery replacement. The hearing assistance system is coupled to a middle ear input transducer and a middle or inner ear output stimulator. The hearing assistance system is capable of use in a partial middle ear implantable (P-MEI), total middle ear implantable (T-MEI), or cochlear implant hearing assistance system.

THE FIELD OF THE INVENTION

This invention relates to an at least partially implantable hearingassistance system or cochlear implant.

BACKGROUND

In some types of partial middle ear implantable (P-MEI) or total middleear implantable (T-MEI) hearing assistance systems, sounds producemechanical vibrations which are transduced by an electromechanical inputtransducer into electrical signals. These electrical signals are in turnprovided to an electronics unit which amplifies the signal and providesit to an electromechanical output transducer. The electromechanicaloutput transducer typically vibrates an ossicular bone in response tothe applied amplified electrical signals, thus improving hearing.

Such systems, as well as other hearing assistance systems, typicallyface limitations on processing capability and longevity due to thelimited energy capacity of implanted batteries. This is particularlytrue for conventional P-MEI hearing assistance systems having a batterydisposed in the electronics unit, which is implanted in the mastoidregion of the temporal bone behind the ear. There is a need in the artfor a hearing assistance system that provides increased batterycapacity, which would ease the limitations on processing capability andlongevity. There is a further need in the art for a hearing assistancesystem that allows convenient battery replacement.

SUMMARY

The present invention provides a hearing assistance system having anelectronics unit that is remotely situated from the ear, therebyrealizing several advantages. The hearing assistance system of thepresent invention includes an electromechanical input transducer, whichis proportioned for disposition within a middle ear region of a firstear, for converting a mechanical sound vibration into an inputelectrical signal. An output stimulator is proportioned for dispositionwithin the middle ear region or an inner ear region of a second ear. Anelectronics unit is proportioned for subcutaneous subcranialimplantation. The electronics unit provides an output electrical signalin response to the input electrical signal. An input link communicatesthe input electrical signal between the input transducer and thesubcranially implanted electronics unit. An output link communicates theoutput electrical signal between the output stimulator and thesubcranially implanted electronics unit.

The first and second ears may be the same ear, or different ears. In oneembodiment, the output stimulator is an electromechanical transducer forconverting an electrical signal into a mechanical sound vibration. Inanother embodiment, the output stimulator is a cochlear implant fordelivering electrical stimuli to the inner ear. The electronics unit is,in one embodiment, proportioned for pectoral implantation.

The hearing assistance system operates according to a method thatincludes receiving a mechanical sound vibration from anelectromechanical input transducer that is proportioned for dispositionwithin a middle ear region of a first ear, and providing an inputelectrical signal in response thereto. The input electrical signal iscommunicated to a subcranially implanted electronics unit that providesan output electrical signal in response thereto. The output electricalsignal is communicated to an output stimulator that is proportioned fordisposition within the middle ear region or an inner ear region of asecond ear. The output stimulator provides output stimuli to the middleor inner ear in response to the output electrical signal.

By providing a hearing assistance system having an electronics unit thatis remotely situated from the ear, a larger volume is available than ifimplanted in the mastoid region of the temporal bone behind the ear. Thelarger electronics unit, in turn, carries therein a larger volume powersource having increased energy capacity. This provides severaladvantages, including: increased longevity of the implantable hearingassistance system before battery replacement is required; moreconvenient battery replacement, such as when the electronics unit ispectorally implanted; and allowing for higher power consumption signalprocessing capabilities.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like numerals describe substantially similar componentsthroughout the several views.

FIG. 1 illustrates a frontal section of an anatomically normal human earin which the invention operates.

FIG. 2 is a generalized schematic illustration of a frontal view of aperson with cutaway views each ear, including one embodiment of theinvention partially disposed in one ear.

FIG. 3 is a generalized schematic illustration of a frontal view of aperson with cutaway views each ear, including a second embodiment of theinvention partially disposed in each ear.

FIG. 4 is a generalized schematic illustration of a frontal view of aperson with cutaway views of each ear, including a third embodiment ofthe invention that is partially disposed in each ear and has dual inputand output paths.

FIG. 5 is a generalized schematic illustration of a frontal view of aperson with cutaway views of each ear, including a fourth embodiment ofthe invention comprising a cochlear implant output stimulator.

DETAILED DESCRIPTION

The invention provides a hearing assistance system capable of use as orwith a middle ear implantable hearing system such as a partial middleear implantable (P-MEI), total middle ear implantable (T-MEI), cochlearimplant, or other hearing system. A P-MEI or T-MEI hearing systemassists the human auditory system in converting acoustic energycontained within sound waves into electrochemical signals delivered tothe brain and interpreted as sound. FIG. 1 illustrates generally a humanauditory system. Sound waves are directed into an external auditorycanal 20 by an outer ear (pinna) 25. The frequency characteristics ofthe sound waves are slightly modified by the resonant characteristics ofthe external auditory canal 20. These sound waves impinge upon thetympanic membrane (eardrum) 30, interposed at the terminus of theexternal auditory canal 20, between it and the tympanic cavity (middleear) 35. Variations in the sound waves produce tympanic vibrations. Themechanical energy of the tympanic vibrations is communicated to theinner ear, comprising cochlea 60, vestibule 61, and semicircular canals62, by a sequence of articulating bones located in the middle ear 35.This sequence of articulating bones is referred to generally as theossicular chain 37. Thus, the tympanic membrane 30 and ossicular chain37 transform acoustic energy in the external auditory canal 20 tomechanical energy at the cochlea 60.

The ossicular chain 37 includes three primary components: a malleus 40,an incus 45, and a stapes 50. The malleus 40 includes manubrium and headportions. The manubrium of the malleus 40 attaches to the tympanicmembrane 30. The head of the malleus 40 articulates with one end of theincus 45. The incus 45 normally couples mechanical energy from thevibrating malleus 40 to the stapes 50. The stapes 50 includes acapitulum portion, comprising a head and a neck, connected to afootplate portion by means of a support crus comprising two crura. Thestapes 50 is disposed in and against a membrane-covered opening on thecochlea 60. This membrane-covered opening between the cochlea 60 andmiddle ear 35 is referred to as the oval window 55. Oval window 55 isconsidered part of cochlea 60 in this patent application. The incus 45articulates the capitulum of the stapes 50 to complete the mechanicaltransmission path.

Normally, prior to implantation of the invention, tympanic vibrationsare mechanically conducted through the malleus 40, incus 45, and stapes50, to the oval window 55. Vibrations at the oval window 55 areconducted into the fluid-filled cochlea 60. These mechanical vibrationsgenerate fluidic motion, thereby transmitting hydraulic energy withinthe cochlea 60. Pressures generated in the cochlea 60 by fluidic motionare accommodated by a second membrane-covered opening on the cochlea 60.This second membrane-covered opening between the cochlea 60 and middleear 35 is referred to as the round window 65. Round window 65 isconsidered part of cochlea 60 in this patent application. Receptor cellsin the cochlea 60 translate the fluidic motion into neural impulseswhich are transmitted to the brain and perceived as sound. However,various disorders of the tympanic membrane 30, ossicular chain 37,and/or cochlea 60 can disrupt or impair normal hearing.

Hearing loss due to damage in the cochlea is referred to assensorineural hearing loss. Hearing loss due to an inability to conductmechanical vibrations through the middle ear is referred to asconductive hearing loss. Some patients have an ossicular chain 37lacking sufficient resiliency to transmit mechanical vibrations betweenthe tympanic membrane 30 and the oval window 55. As a result, fluidicmotion in the cochlea 60 is attenuated. Thus, receptor cells in thecochlea 60 do not receive adequate mechanical stimulation. Damagedelements of ossicular chain 37 may also interrupt transmission ofmechanical vibrations between the tympanic membrane 30 and the ovalwindow 55.

Various techniques have been developed to remedy hearing loss resultingfrom conductive or sensorineural hearing disorder. For example,tympanoplasty is used to surgically reconstruct the tympanic membrane 30and establish ossicular continuity from the tympanic membrane 30 to theoval window 55. Various passive mechanical prostheses and implantationtechniques have been developed in connection with reconstructive surgeryof the middle ear 35 for patients with damaged elements of ossicularchain 37. Two basic forms of prosthesis are available: total ossicularreplacement prostheses (TORP), which is connected between the tympanicmembrane 30 and the oval window 55; and partial ossicular replacementprostheses (PORP), which is positioned between the tympanic membrane 30and the stapes 50.

Various types of hearing aids have been developed to compensate forhearing disorders. A conventional "air conduction" hearing aid issometimes used to overcome hearing loss due to sensorineural cochleardamage or mild conductive impediments to the ossicular chain 37.Conventional hearing aids utilize a microphone, which transduces soundinto an electrical signal. Amplification circuitry amplifies theelectrical signal. A speaker transduces the amplified electrical signalinto acoustic energy transmitted to the tympanic membrane 30. However,some of the transmitted acoustic energy is typically detected by themicrophone, resulting in a feedback signal which degrades sound quality.Conventional hearing aids also often suffer from a significant amount ofsignal distortion.

Implantable hearing systems have also been developed, utilizing variousapproaches to compensate for hearing disorders. For example, cochlearimplant techniques implement an inner ear hearing system. Cochlearimplants electrically stimulate auditory nerve fibers within the cochlea60. A typical cochlear implant system includes an external microphone,an external signal processor, and an external transmitter, as well as animplanted receiver and an implanted single channel or multichannelprobe. A single channel probe has one electrode. A multichannel probehas an array of several electrodes. In the more advanced multichannelcochlear implant, a signal processor converts speech signals transducedby the microphone into a series of sequential electrical pulsescorresponding to different frequency bands within a speech frequencyspectrum. Electrical pulses corresponding to low frequency sounds aredelivered to electrodes that are more apical in the cochlea 60.Electrical pulses corresponding to high frequency sounds are deliveredto electrodes that are more basal in the cochlea 60. The nerve fibersstimulated by the electrodes of the cochlear implant probe transmitneural impulses to the brain, where these neural impulses areinterpreted as sound.

Other inner ear hearing systems have been developed to aid patientswithout an intact tympanic membrane 30, upon which "air conduction"hearing aids depend. For example, temporal bone conduction hearingsystems produce mechanical vibrations that are coupled to the cochlea 60via a temporal bone in the skull. In such temporal bone conductionhearing systems, a vibrating element can be implemented percutaneouslyor subcutaneously.

A particularly interesting class of hearing systems includes those whichare configured for disposition principally within the middle ear 35space. In middle ear implantable (MEI) hearing assistance systems, anelectrical-to-mechanical output transducer couples mechanical vibrationsto the ossicular chain 37, which is optionally interrupted to allowcoupling of the mechanical vibrations to the ossicular chain 37. Bothelectromagnetic and piezoelectric output transducers have been used toeffect the mechanical vibrations upon the ossicular chain 37.

One example of a partial middle ear implantable (P-MEI) hearing systemhaving an electromagnetic output transducer comprises: an externalmicrophone transducing sound into electrical signals; externalamplification and modulation circuitry; and an external radio frequency(RF) transmitter for transdermal RF communication of an electricalsignal. An implanted receiver detects and rectifies the transmittedsignal, driving an implanted coil in constant current mode. A resultingmagnetic field from the implanted drive coil vibrates an implantedmagnet that is permanently affixed only to the incus 45. Suchelectromagnetic output transducers have relatively high powerconsumption requiring larger batteries, which limits their usefulness intotal middle ear implantable (T-MEI) hearing systems.

A piezoelectric output transducer is also capable of effectingmechanical vibrations to the ossicular chain 37. An example of such adevice is disclosed in U.S. Pat. No. 4,729,366, issued to D. W. Schaeferon Mar. 8, 1988. In the '366 patent, a mechanical-to-electricalpiezoelectric input transducer is associated with the malleus 40,transducing mechanical energy into an electrical signal, which isamplified and further processed by an electronics unit. A resultingelectrical signal is provided to an electrical-to-mechanicalpiezoelectric output transducer that generates a mechanical vibrationcoupled to an element of the ossicular chain 37 or to the oval window 55or round window 65. In the '366 patent, the ossicular chain 37 isinterrupted by removal of the incus 45. Removal of the incus 45 preventsthe mechanical vibrations delivered by the piezoelectric outputtransducer from mechanically feeding back to the piezoelectric inputtransducer.

In the '366 patent, a power source and electronic circuits are disposedin a surgically developed antrum in the mastoid bone of the subject'sskull. A limited volume is available for creating such a cavity. As aresult, the volume and energy capacity of the power source iscorrespondingly limited as well. This limits both processing capabilityand longevity of such a device. Furthermore, it is inconvenient toreplace the power source since it is implanted in the mastoid bone.

The present invention provides a hearing assistance system having anelectronics unit that is remotely situated from the ear, therebyrealizing several advantages as explained below. The invention iscapable of use as or with a MEl hearing assistance system, such as aP-MEI or T-MEI hearing assistance system. The invention is also capableof use with a variety of piezoelectric, electromagnetic, and othertransducers. The invention is also capable of use as or with a cochlearimplant system, such as a single channel or multichannel cochlearimplant, or other cochlear implant.

FIG. 2 is a generalized schematic illustration of one embodiment of theinvention. FIG. 2 illustrates a frontal view of a person with cutawayviews of the anatomical features of each of a right ear 200 and a leftear 205. An electromechanical input transducer 210 is disposed withinthe middle ear 35 region of right ear 200. In one embodiment, inputtransducer 210 is mechanically coupled, such as to tympanic membrane 30,malleus 40, incus 45, or other auditory element, for receivingmechanical sound vibrations that are converted into an input electricalsignal. In another embodiment, input transducer 210 is a microphone forreceiving sound vibrations that are converted into the input electricalsignal. An output stimulator, such as electromechanical outputtransducer 215 is disposed within middle ear 35 region of right ear 200,and mechanically coupled to an auditory element such as stapes 50.

Input and output transducers 210 and 215, respectively, are eitherfreestandingly coupled to their respective auditory elements, or alsorigidly mounted elsewhere, such as to the temporal bone in the middleear 35 region. Input transducer 210 typically includes at least onepiezoelectric element such as a piezoelectric crystal, ceramic, orpolymer. Output transducer 215 typically includes at least one similarpiezoelectric element, or an electromagnetic or other suitabletransducer type. Incus 45 is optionally removed to prevent mechanicalfeedback from output transducer 215 to input transducer 210 throughincus 45.

Electronics unit 225 is remotely disposed from input transducer 210 andoutput transducer 215. More particularly, electronics unit 225 islocated away from the middle ear and away from the mastoid region of thetemporal bone. Instead, electronics unit 225 is typically subcraniallyimplanted. For example, electronics unit 225 is typically proportionedfor implantation in the person's pectoral region, or some otherconvenient location. Electronics unit 225 typically contains a powersource 230, such as a battery, and signal processing unit 235. Sinceelectronics unit 225 of the present invention need not be implanted inthe mastoid region of the temporal bone, its volume may be increased.

For example, implantation in the mastoid region of the temporal bonetypically limits the volume of electronics unit 225 to approximately 2cubic centimeters. Since electronics unit 225 of the present inventionneed not be implanted in the mastoid region of the temporal bone, itsvolume may be increased, such as to exceed approximately 10 cubiccentimeters. Power source 230, contained within electronics unit 225,may correspondingly increase in both volume and energy capacity. Currentbattery technology typically has a volumetric energy density limited toapproximately 0.4 ampere-hours per cubic centimeter. If the power sourceoccupies most of the volume the electronics unit in which it iscontained, then battery capacity would be limited to approximately 0.8ampere-hours when implanted in the mastoid region of the temporal bone.Battery capacity increases to approximately 4 ampere-hours whenimplanted in the pectoral or other region, according to the presentinvention. Assuming the electronics unit requires 20 microamperes foroperation, the increased battery capacity translates into an increase indevice longevity from approximately 4.5 years to approximately 22 years.Thus, the present invention is capable of providing a power sourcehaving an energy capacity well exceeding 1 ampere-hour, as explainedabove.

The increased energy capacity of power source 230 may be used toincrease the implanted longevity of the hearing assistance system beforereplacement of power source 230 is needed. Alternatively, higher powerconsumption functionality may be incorporated in signal processing unit235. For example, a digital signal processor may be included in signalprocessing unit 235. The increased energy capacity of power source 230may also be used to achieve some combination of increased longevity andhigher power consumption functionality. When subcranially implanted inthe pectoral region, electronics unit 225 is easier to explant than whendisposed in the mastoid portion of the temporal bone. This simplifiesthe procedure of replacing power source 230 when its useful energycapacity is exhausted.

In one embodiment, input transducer 210 is electrically coupled throughan input link, such as input lead 236, for providing the inputelectrical signal to electronics unit 225. Similarly, electronics unit225 is electrically coupled through an output link, such as output lead237, for providing the output electrical signal to the outputstimulator, such as output transducer 215. Input and output leads 236and 237, respectively, are typically implemented separately, although asingle integrally formed lead could be used to combine input and outputleads 236 and 237, respectively.

In one embodiment, at least one of input and output leads 236 and 237provides AC coupled communication, such as by a series capacitor,between electronics unit 225 and at least one of input transducer 210and the output stimulator, such as output transducer 215. Such ACcoupled communication is advantageous in reducing or eliminatingpotential dendrite growth, which is the formation of tissue occurringwhen a DC electric field is passed through bodily fluids. Such dendritesare typically conductive and might degrade performance of the inputtransducer 210 and the output stimulator, such as output transducer 215,or other circuits.

Input and output leads 236 and 237 are subcutaneously disposed. Forexample, in one embodiment where electronics unit 225 is pectorallyimplanted, input and output leads 236 and 237 extend subcutaneously fromthe pectoral region, along the neck region, and through an access holecreated in a mastoid portion of the temporal bone anterior to outer ear20 region of right ear 200.

In one embodiment, input and output leads 236 and 237, respectively, areindividually mechanically coupled to receptacles on respective input andoutput transducers 210 and 215. In another embodiment, input and outputleads 236 and 237, respectively, are mechanically coupled to receptacleson the one or more mounts to which respective input and outputtransducers 210 and 215 are affixed, and the receptacles areindividually electrically coupled to one of input and output transducers210 and 215, respectively. In another embodiment, respective input andoutput leads 236 and 237 are mechanically coupled to a coupleroptionally located outside middle ear 35 region for more convenientaccess, and the coupler is itself individually electrically coupled toeach one of the input and output transducers 210 and 214, respectively.

In one embodiment, respective input and output leads 236 and 237 areeach longer than 2 inches. More particularly, the input and output leads236 and 237, respectively, will extend from electronics unit 225, whichis remotely implanted such as in the pectoral region, and an middle ear35 or inner ear region on the same or opposite side of the subject'sbody. Input and output leads 236 and 237, respectively, will typicallyrange from between 2 inches and 12 inches in length, but these lengthswill vary according to individual physiology and exact location of theimplanted electronics unit 225.

Input and output leads 236 and 237, respectively, include at least one,and typically more than one, conductor that is capable of withstandingflexion stresses such as from muscle movement. For example, theconductors may be of nickel alloy wires manufactured with adrawn-brazed-strand (DBS) technique to resist flexion related fractures,although other suitable conductor materials and manufacturing techniquesmay also be used. The conductors are typically insulated from each otherand from the subject's body by insulation comprising silicone rubber orother suitable insulation material. Input and output leads 236 and 237,respectively, may also include connectors for engaging receptacles oninput and output transducers 210 and 215, respectively, or on associatedmounts or couplers, and also for engaging receptacles on electronicsunit 225.

FIG. 3 is a generalized schematic illustration of another embodiment ofthe invention including a frontal view of a person in which it is used.In FIG. 3, input transducer 210 is disposed within middle ear 35 ofright ear 200 and output transducer 215 is disposed within middle ear 35of left ear 205, or vice-versa, using similar techniques to thosedescribed above. Input and output transducers 210 and 215 arerespectively coupled through input lead 236 and output lead 237 toelectronics unit 225 in a similar manner as described above. Theembodiment of FIG. 3 is particularly useful when right ear 200 hassevere sensorineural hearing loss such that the output stimulatorprovides it with no benefit. In that case, mechanical sound vibrationsreceived in the right ear 200 may be communicated to the left ear 205for output stimulation and interpretation by the subject's auditorysystem.

FIG. 4 is a generalized schematic illustration of another embodiment ofthe invention including a frontal view of a person in which it is used.FIG. 4 includes the features of the present invention with respect tothe right ear 200, as illustrated in FIG. 2, and adds similar featureswith respect to the left ear 205. More particularly, additionalinstances of input and output transducers 210 and 215, respectively, aredisposed in left ear 205, and electrically coupled to electronics unit225 through input and output links such as the respective instances ofinput and output leads 236 and 237 associated with left ear 205. In thisembodiment, the invention implements a dual path hearing assistancesystem. One example of dual path hearing assistance system functionalityis described in co-pending patent application entitled DUAL PATHIMPLANTABLE HEARING ASSISTANCE DEVICE, filed on even date with thepresent application, assigned to the assignee of the presentapplication, and which is herein incorporated by reference.

FIG. 5 is a generalized schematic illustration of another embodiment ofthe invention including a frontal view of a person in which it is used.FIG. 5 includes some of the features of the invention described withrespect to FIG. 2, but the output stimulator comprises a single channelor multiple channel cochlear implant 250 rather than output transducer215. Cochlear implant 250 is disposed in cochlea 60 by insertion eitherthrough the oval window 55, round window 65, or elsewhere, or disposedelsewhere in the inner ear region. In this embodiment, signal processingunit 235 includes cochlear implant processing capability, and outputlead 237 includes an appropriate configuration of conductorscorresponding to the particular single channel or multiple channelcochlear implant 250.

Thus, the present invention provides an implantable hearing assistancesystem having an implantable electronics unit that is remotely situatedfrom the ear, rather than implanted in the mastoid portion of thetemporal bone. The increased volume available in the remote electronicsunit allows a power source contained therein, which has increased energycapacity. This improves longevity, enhances processing capability, andsimplifies battery replacement.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reviewing the abovedescription. The scope of the invention should, therefore, be determinedwith reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

What is claimed is:
 1. A hearing assistance system comprising:anelectromechanical input transducer, proportioned for disposition withina middle ear region of a first ear, for converting a mechanical soundvibration into an input electrical signal; an output stimulator,proportioned for disposition within the middle ear region of the firstear; and an electronics unit having volume exceeding approximatelv 10cubic centimeters, electrically connected between the input transducerand the output stimulator and proportioned only for subcutaneouspectoral implantation, wherein the electronics unit receives the inputelectrical signal from the input transducer and provides an outputelectrical signal to the output stimulator in response to the inputelectrical signal.
 2. The hearing assistance system of claim 1, whereinthe output stimulator is an electromechanical transducer for convertingan electrical signal into a mechanical sound vibration.
 3. The hearingassistance system of claim 1, wherein the output stimulator is acochlear implant for delivering electrical stimuli to the inner ear. 4.The hearing assistance system of claim 1, and further comprising:aninput link electrically connecting the input transducer to theelectronics unit and an output link electrically connecting theelectronics unit to the output stimulator, wherein each of the input andoutput links includes an implantable lead.
 5. The hearing assistancesystem of claim 4, wherein at least one implantable lead of the inputand output links is longer than approximately 2 inches.
 6. The hearingassistance system of claim 4, wherein at least one implantable lead ofthe input and output links comprises first and second lead wires.
 7. Thehearing assistance system of claim 4, wherein at least one implantablelead of the input and output links comprises first and second lead wiresthat are twisted with each other.
 8. The hearing assistance system ofclaim 4, wherein at least one implantable lead of the input and outputlinks comprises at least one shielded lead wire.
 9. The hearingassistance system of claim 1, and further comprising:an input linkelectrically connecting the input transducer to the electronics unit andan output link electrically connecting the electronics unit to theoutput stimulator, wherein at least one of the input and output links iscapable of alternating current coupled communication.
 10. The hearingassistance system of claim 1, wherein the electronics unit includes apower source.
 11. The hearing assistance system of claim 10, wherein thepower source includes a battery having capacity exceeding 1 ampere-hour.12. The hearing assistance system of claim 1, wherein the electronicsunit includes a digital signal processor.
 13. The hearing assistancesystem of claim 1, wherein the electronics unit includes a telemetrydevice for communicating with an external telemetry unit.
 14. Thehearing assistance system of claim 1, wherein the middle ear region inwhich the input transducer and output stimulator are proportioned fordisposition is a naturally present cavity.
 15. A hearing assistancesystem comprising:an electromechanical input transducer, proportionedfor disposition within a middle ear region of a first ear, forconverting a mechanical sound vibration into an input electrical signal;an output stimulator, proportioned for disposition within the middle earregion of the first ear; an electronics unit having a volume exceedingapproximatelv 10 cubic centimeters, proportioned only for subcutaneouspectoral implantation remotely from the input transducer and the outputstimulator, that provides an output electrical signal in response to theinput electrical signal; an input link electrically connecting the inputtransducer to the electronics unit for communicating the inputelectrical signal between the input transducer and the electronics unit;and an output link electrically connecting the output stimulator to theelectronics unit for communicating the output electrical signal betweenthe output stimulator and the electronics unit.
 16. The system of claim1 wherein the electromechanical input transducer is configured andarranged for connection to a tympanic membrane, a malleus, or an incusof the middle ear region of the first ear.
 17. The system of cliam 1wherein the output stimulator is configured and arranged for connectionto a stapes of the middle ear region of the first ear or a cochlea ofthe inner ear region of the first ear.
 18. A hearing assistance systemcomprising:an electromechanical input transducer, proportioned fordisposition within a middle ear region of a first ear, for converting amechanical sound vibration into an input electrical signal; an outputstimulator, proportioned for disposition within at least one of themiddle ear region and an inner ear region of a second ear; and anelectronics unit having a volume exceeding approximately 10 cubiccentimeters, electrically connected between the input transducer and theoutput stimulator and proportioned only for subcutaneous pectoralimplantation, wherein the electronics unit receives the input electricalsignal from the input transducer in the first ear and provides an outputelectrical signal to the output stimulator in the second ear in responseto the input electrical signal.